"My last girlfriend didn't work out super well," Dietzen tells TVGuide.com, referring to Agent Michelle Lee (Liza Lapira), the NCIS mole who died after Gibbs (Mark Harmon) shot her in Season 6. "It lasted a while, but every time your girlfriend ends up being a double agent or getting shot by your boss, it's hard to handle for your personal confidence."Don't worry: Jimmy's new girlfriend isn't going anywhere, and even makes a brief appearance in Tuesday's episode. "The episode shows Jimmy showing Ziva [Cote de Pablo] and Tony [Michael Weatherly] and McGee [Sean Murray] photos of his many dates with his new girl," Dietzen says. "He's showing off some risqué photos from when they went to a tattoo parlor together. You'll be seeing some skin in this next episode. It's pretty ridiculous but it's pretty fun.

Elsewhere in the episode, NCIS viewers will see a first: Gibbs and Fornell (returning guest star Joe Spano) look into an NCIS polygraph specialist's connection to a murder, and Gibbs submits to a polygraph test."There are some pretty tough questions," Dietzen says. "He's done things in the past that he doesn't talk about and he doesn't want anyone to know about. So, if any of those things were to come up and he is strapped to a lie detector, where does he go from there?"As for Jimmy's love interest, Dietzen says he thinks she has staying power. "The writers seem to like her because she's mentioned several times over the course of the season," Dietzen says. "Jimmy's mind is drifting to her quite often now, and it gives something for the rest of the team to talk about. The only bummer is Jimmy's got nobody to double date with on the team."

Dietzen has promised fans via his newly activated Twitter account that Jimmy will pop up in four of this season's final five episodes."True fans will love how this is building up to the end," Dietzen says. "If you really look at it, it's a five-part finale. There are nuggets of the story dedicated to how this season is going to end, so you can't miss any of it."NCIS returns Tuesday at 8/7c on CBS.